This application is based on Japanese patent application No. 10-291041 filed on Oct. 13, 1998, the entire contents of which are incorporated herein by reference.
a) Field of the Invention
The present invention relates to a communications apparatus and more particularly to a communications apparatus with light emitting elements.
b) Description of the Related Art
There are technical trends for latest personal computers to mount digital serial communication interfaces such as IEEE 1394 specifications and universal serial buses (USB).
FIG. 6 shows an example of the structure of a communications network of IEEE 1394 specifications. Four nodes ND1 to ND4 are communications apparatuses having a communication interface and connected. by communication cables CBL.
A general communication cable has signal (data) lines. A communication cable of IEEE 1394 and USB is characterized in that it has power supply lines as well as signal lines. Since the communication cable has power supply lines, communications are possible even if the power switches of not all the nodes ND1 to ND4 are turned off. The nodes ND1 to ND4 can communicate with each other while receiving a power from the power supply lines of the communication cables.
For example, even if the power switches of the nodes ND1, ND3 and ND4 are turned on and the power switch of the node ND2 is turned off, communications between the nodes ND1 and ND4 are possible. In this case, the node ND2 operates as a repeater while receiving a power from the power supply lines 17 of the communication cables CBL. Namely, the node ND2 can relay a signal between the nodes ND1 and ND3.
A communications modem has light emitting diodes (LED) for displaying a communication state. A hard disk drive and a floppy disk drive have a light emitting diode for displaying an access state to a storage medium. If a communications apparatus is provided with a light emitting diode for displaying a communication state, a user can conveniently recognize the communication state.
If the power switch of a communications modem, a hard disk drive or the like is turned off, the light emitting diode cannot emit light. In this case, since a communications modem, a hard disk drive or the like does not perform communications while the power switch is turned off, it poses any practical problem even if the communication state is not displayed.
In IEEE 1394 or the like, even if the power switch of, for example, the node ND2 is turned off, the node ND2 operates as a repeater. Therefore, the communication state of the node ND2 is sometimes desired to be confirmed. However, in this case, it is difficult to drive light emitting diodes of the node ND2 when the power switch of the node ND2 is turned off. It is desired to know the communication state of the node ND2 even if the power switch of the node ND2 is turned off.
It is an object of the present invention to provide a communications apparatus capable of displaying a communication state even if the power of the apparatus is turned off.
According to one aspect of the present invention, there is provided a communications apparatus comprising: a communication cable receptacle having signal terminals and power supply terminals for connection to a communication cable having signal lines and power supply lines; a communication interface for transferring a signal to and from an external via the signal terminals of the communication cable receptacle; and one or a plurality of light emitting elements capable of emitting light, the light emitting element being selectively connected to the power supply terminals of the communication cable receptacle and receiving a power from the communication cable via the power supply terminals.
According to another aspect of the invention, there is provided a communications apparatus comprising: a communication cable receptacle having signal terminals and power supply terminals for connection to a communication cable having signal lines and power supply lines; a communication interface for transferring a signal to and from an external via the signal terminals of the communication cable receptacle; and one or a plurality of light emitting elements capable of emitting light, the light emitting element being disposed near the communication cable receptacle, being selectively connected to the power supply terminals of the communication cable receptacle, and being capable of displaying at least one of a communication state, a state of the apparatus, an alarm state, and a connection state of the apparatus while receiving a power from the communication cable via the power supply terminals.
Since the light emitting element can receive a power from an external via the power supply terminals of the communication cable receptacle, it can emit light even if the power cannot be supplied from the communications apparatus.
Even if the power cannot be supplied from the communications apparatus, the state such as the communication state can be displayed so that a user can always and conveniently confirm the communication state.